I dont know whether I'm suffering from HPPD or not, but I have similar issues which I can relate to HPPD.
A month back I smoked weed for the first time in my life, it was a bad experience resulting in increased heart rate & almost a blackout feeling, but I somehow managed it and it got better. But after this experience, my school tests started so I started staying sleepless and more on coffees.
I never thought twice about that experience after weed, and everything was normal until next week I took a medicine called 'Solvin cold' which resulted in a similar experience which consisted of high pulse rate, high Blood pressure and great anxiety and visual problems which included shape distortion, blurred vision, everything seeming dull, but lights are being very intensified. Itchiness inside my head, and basically I'm feeling like I'm tripping always. This is really tough to live with. I'm on anti-depressants and anti-anxiety pills for now. I've undergone a drug test also for cannabis, but it came negative. Please help me in diagnosis of the condition and treatment or I would die. Not really die, but it is tough to live with.